1. Field of the Invention
The invention relates to a process for preparing a high-molecular-weight polyester by reacting an organic dicarboxylic acid or derivatives thereof with a mixture of alkane- or alkenediols with substantial exclusion of oxygen, in the presence of a condensation catalyst.
2. Discussion of the Background
High-molecular-weight polyesters are excellent materials having specific properties which enable them to be used as raw material for strong high-tech products. It is typical of this application area that frequently, judged according to industrial criteria, relatively small amounts having an exactly prescribed high molecular weight are required.
Since, in large-scale production, polyesters are obtained continuously or batchwise in large amounts having a uniform molecular weight, it is usually uneconomical and also technically difficult to make available fractional amounts having a defined high-molecular weight.
Polyesters having a high molecular weight are conventionally known from the prior art. They contain, inter alia, moieties of unsaturated monomer components which may, if desired, be crosslinked with thermolabile compounds (DE-OS 25 09 726; 25 09 790; 25 52 424). It is characteristic of the conventional polyesters that the final molecular weight has to be set as the polyester is being synthesized. A subsequent manipulation of the molecular weight is impossible or leads to a deterioration in product properties.
It is also known from the prior art to subject polyesters to a solid-phase post-condensation. However, this usually requires relatively long times. Furthermore, only a small increase in the viscosity is achieved.